Transwiki:Manual transmission driving technique

The Friction Point

• With the shifter in neutral, push the clutch all the way down with your left foot and start the engine.
• After the engine starts, wait for engine speed to return to idle.
• Shift to 1st gear, then slowly release the clutch without touching the accelerator. Stop any pedal movement when the engine's RPM dips slightly. The clutch is at the friction point since the clutch plate begins to experience friction as it presses against the flywheel.
• Push the clutch down to the floor and practice releasing to the friction point a few times. Note how the clutch pedal and engine's RPM changes, if any.

Moving For The First Time

While on level ground, where you should be when you learn to drive a manual, follow the steps below

• Push the clutch all the way down, shift to first gear, and release the parking brake.
• Release the clutch to the friction point. The car should begin to move.
• If it doesn't, touch the gas pedal to raise the engine speed slightly. Ease the pressure off of the clutch pedal slightly until the car moves. Then stop any pedal movements.
• Wait about 2 seconds, then completely release the clutch.

Get Going Faster

The car moves because the engine is losing a bit of its momentum. Although it burns fuel to recover lost momentum, the engine stops running if it loses too much (see stalling below). If we want to get going faster, we need to get more momentum from the engine by releasing the clutch faster. At the same time, we have to add more gas so the engine can recover that momentum to keep running. The steps are similar to the above until you get to the friction point.

• Once you are at the friction point, add a small amount of gas without moving the clutch pedal. The engine should raise its speed slightly.
• Ease the pressure off of the clutch until the engine slows down a bit. The car should be moving noticeably at this point.
• Hold the pedals steady for about one second, then completely release the clutch.

A beginner should concentrate on performing these skills smoothly. Once smoothness is mastered, practicing coordination is the next goal. As the engine speed rises, a competent driver would ease off of the clutch just enough to stop the engine speed from rising further. That would get the vehicle moving even quicker. Once the car starts moving, stop any pedal movements for about one second before completely releasing the clutch.

Shifting Concepts

In a manual transmission car, the driver is responsible for operating a clutch and changing what gear the car is in using a gear shifter. The driver is required to correctly operate these two devices in order to start, accelerate, decelerate and stop the car.

The basic concept of shifting is to allow the car's engine to turn the wheels at one of several different gear ratios. Each gear has a fairly wide range of vehicle speeds that it covers, with plenty of overlap between the gears, except at extreme vehicle speeds. Near the limits of the car's speed, the speed of the car dictates the gear ratio. If the vehicle is to move at the slowest possible crawling pace with the engine engaged, that requires the lowest gear to be selected; the engine will stall in any other gear (if it does not, it is not the slowest possible crawling speed!). At the car's top speed, it may be necessary to be in the highest gear, so that the engine does not spin beyond its "redline" limit. This basic connection between gear ratios and speeds is why gears are sometimes called "speeds", as in "five speed transmission".

At the intermediate speeds not near the limits, the driver has a choice of two or more possible gear ratios. As a rule of thumb, a lower gear from among these, possibly the lowest, is chosen when power is required in order to accelerate or to climb a hill, or to provide "engine braking" to reduce or prevent unwanted acceleration when driving downhill. Higher gears are chosen when less power or less engine braking is required, in order to save fuel, reduce engine wear and minimize noise.

Before the driver can change gears, the clutch must be disengaged. The clutch is a mechanism that temporarily disengages the transmission and drivetrain from the engine of the vehicle. Once the clutch is depressed the driver can change gears without disrupting the smooth motion of the vehicle. When the car is in the desired gear, the driver then releases the clutch to allow the engine to turn the wheels again.

If the gear is changed without depressing the clutch, the gears may grind which can cause damage to the transmission. If a gear that is too low is selected, the wheels may be spinning too fast for the clutch to catch, again grinding the gears. Alternatively, if the clutch does catch the engine may be forced to spin faster than it is capable of which can damage the engine. If a gear that is too high is selected, the gearing ratio will force the engine to rotate at a speed that is too slow and the engine may stall.

Upshifting

When accelerating in any forward gear other than top gear, shift up when the engine is turning at too high a speed for the current gear. The engine speed that constitutes "too high" varies from vehicle to vehicle and according to the driver's taste, but the absolute upper limit is usually marked on most vehicles equipped with a tachometer as a red area called the redline. Running the engine past this speed can cause damage to internal components of the engine (and most modern cars with electronic engine control computers will not permit the engine to be run past the redline). In practice, one usually shifts up well before the engine speed reaches redline. The vehicle's owner's manual should contain a table of recommended upshift speeds, but as a general rule of thumb, consider shifting between 2000 and 3000 rpm - although in some small engines that make power higher in the rev band shifting around 3500rpm can drop you to a better part of the power band in the next gear. This can be quite different for different cars, as a rule of thumb its a good idea to shift up around 500rpm above the revs the engine does in top gear at 100kph^{[citation needed]} (Note that in a diesel you will usually have to shift at a lower rpm, and the redline is likely to be lower.)

For maximum acceleration, one may shift just before reaching the redline, but for ordinary driving, to conserve fuel, one should shift between a little above the engine's maximum torque speed and the lowest engine speed possible without "lugging" the engine. With practice, you will be able to tell when to do this by the sound of the engine.

To upshift:

• Release the accelerator pedal. Alternatively, if you are experienced enough to shift quickly, you may be able to partially release and then reapply the accelerator pedal at the same time as declutching and shifting.
• Press and hold the clutch pedal with your left foot.
• Reapply throttle to a level appropriate for the higher gear. If you are experienced enough to shift quickly and smoothly, you may be able to partially release the accelerator pedal while shifting, and the engine will roughly synchronise. Alternatively if you shift quickly enough, reapply the throttle after reengaging the clutch.
• Move the gear shift knob, depending on the gear that is currently selected:
  • To shift from an odd-numbered gear (i.e. 1st or 3rd) into the next highest gear, move the shift knob down, through neutral, to the corresponding position on the bottom row.
  • To shift from an even-numbered gear (i.e. 2nd or 4th) into the next highest gear, move the shift knob up to neutral, one column to the right, then up to the new position on the top row.
• Smoothly release the clutch pedal, allowing the new, lower engine speed to match up with the vehicle's speed.

If you take longer than a second or so to upshift, the engine will probably have slowed down too much for the new gear, and the car will probably jerk backward a bit unless you increase throttle to compensate. Don't increase the throttle too much though, or the engine will be going too fast for the new gear and the car will jerk forward. Once your skill at "matching revs" improves you can release the clutch pedal more quickly without any jerkiness.

Downshifting

When decelerating in any gear above second gear, shift down when the engine is turning at too low a speed for the current gear. The speed that constitutes "too low" varies among vehicles, and you can afford to keep it in a higher gear if little acceleration is needed, but as a rule of thumb, consider downshifting when the engine reaches 1500 RPM. With some practice, you will be able to hear the engine speed and make this judgement.

Although rapid acceleration is never really necessary, it often saves time, can sometimes help to merge into moving traffic and is enjoyable to some people. For rapid acceleration or to climb a steep grade, while the car is already moving in a higher gear, one downshifts, to increase the engine's revs to a point at which it can produce more power. (Beginners may prefer to stop and shift into first before climbing a hill.)

If you notice the RPM decreasing steadily to a low value while climbing a steep hill, despite having a firm foot on the throttle, you should immediately switch to a lower gear or the car may stall and roll down the hill.

It is important not to shift into too low a gear for the car's speed: for instance, shifting into second at highway speeds. Firstly, it should be known that this is bad for the transmission even before the clutch is released. Downshifting into a low gear at high speed causes the input side of the transmission (which connects to the engine via the clutch) to spin excessively fast, possibly much faster than the maximum redline of the engine. This creates stresses in the machinery, and also undue wear on the synchronizers which are doing the job of spinning up the input shaft. Of course, if the clutch is engaged while the transmission input shaft is spinning beyond the engine's "red line", the engine will likely be severely damaged. (In this case, even the engine control computer's rev-limiting function cannot help, as the engine is being driven by the momentum of the car). It is always safe to downshift to the next lower gear when the engine is turning at too low a speed for the current gear. If you "miss" a downshift and hear the engine revving too fast as you let out the clutch, immediately push the clutch back in and shift into a higher gear. Also, pay attention to signs of missing a downshift even before the clutch is released. It takes time to spin up the transmission input shaft to an excessive RPM, and so the stick is more difficult to push into gear if the wrong gear is selected. Also, there may be an audible high pitched whine, similar to an electric drill, as parts of the transmission spin up to a high RPM during the shift.

Due to the larger differences in gear ratio between first and second gear, it's usually best not to downshift into first gear unless you plan to be driving very slowly for some time. Instead, stay in second gear and disengage the clutch when you're about to come to a stop. In some special cases (very steep slopes, crawling traffic) first gear can be useful, however. In some vehicles, it is easier to shift into first gear from a stop than to downshift from second.

To downshift:

• Release the accelerator pedal, unless you are skilled enough to only partially reduce the throttle.
• Press and hold the clutch pedal with your left foot.
• Reapply throttle to a level appropriate for the current speed of travel in the lower gear. This is (somewhat) optional, since gradually releasing the clutch will adjust for a slight mismatch, however if you completely release the accelerator while at the same time shifting too slowly you are likely to have the car jerk somewhat.
• Move the gear shift knob, depending on the gear that is currently selected:
  • To shift from an even-numbered gear (i.e. 2nd or 4th) into the next lowest gear, move the shift knob up, through neutral, to the corresponding position on the top row.
  • To shift from an odd-numbered gear (i.e. 3rd or 5th) into the next lowest gear, move the shift knob down to neutral, one column to the left, then down to the new position on the bottom row.
• Gradually release the clutch pedal, allowing the new, higher engine speed to match up with the vehicle's speed.
• Adjust the throttle as necessary to decrease, maintain, or increase vehicle speed.

If you don't match the engine's speed properly for the lower gear, the car will probably jerk a bit. Once your skill at "matching revs" improves you can release the clutch pedal more quickly without any jerkiness.

Putting it All Together

In actual driving, the individually learned skills of modulating engine torque with the clutch and shifting gears are performed together. Decisions are made on-the-fly and sometimes they have to be canceled or pre-empted as predictions about traffic dynamics turn out to be incorrect. It takes several months of practice before the skills are nearly internalized, and anywhere up to a year of daily driving to become a completely smooth, confident, manual transmission driver who ensures that the machine is always in the correct state in every situation. These are a few tips beyond starting, stopping and shifting:

Sharp Turns

Situation: The driver wishes to turn at an upcoming corner. Coming to a full stop is not required.

Corners are taken at a fairly slow speed, which corresponds to the typical car's second gear: some 30 km/h or even slower. This means that accelerating out of the corner will require the transmission to be in second gear.

The steps are:

• The driver applies pressure to the brake pedal to slow the vehicle down, leaving the transmission in whatever gear it is in.
• Moments before approaching the corner, the car should be travelling at a speed in which second gear may be selected. The driver presses the clutch all the way to the floor and shifts into second gear.
• The clutch is released to complete the shift just before the steering is turned to execute the turn.
• Through the turn, the transmission remains in second gear.
• Coming out the turn, the driver begins to accelerate and straighten the steering.
• By the time the driver shifts to third gear, the car is travelling straight.

By avoiding a transmission shift in the turn itself, the driver can steer with both hands. In some countries or states—such as British Columbia, Canada—if a new driver takes a licensing road test in a manual transmission, points are deducted for shifting in a turn, because there are safety issues with doing so.

Slow-Moving Traffic

Situation: the driver finds himself or herself in a heavily congested flow of traffic. Sometimes the cars ahead come to a full stop. In between stops they sometimes crawl at approximately a walking pace, and at other times speed up substantially only to rapidly slow down again.

In this situation, stressful for a new manual transmission driver, it is important that the driver remain calm and focused. The driver must remember that to prevent the engine from stalling at any time, all that is required is to depress the clutch pedal all the way down.

The trick is to keep moving smoothly while maintaining a generous gap to the next car, and stop and resume if necessary. It should all be done without slipping the clutch.

The driver should monitor the traffic as far ahead as visibility allows, to anticipate whether a complete stop is about to become necessary.

The driver should keep the transmission in second gear if possible and apply a light pressure to the accelerator pedal so that the vehicle slowly crawls forward. In first and second gear, particularly in first, the car is capable of moving very slowly without the engine stalling, or the necessity to slip the clutch. The manual transmission driver must learn to recognize situations in which it's useful to crawl slowly, and take advantage of the transmissions and engine's ability to do so.

But if an impending full stop is anticipated, the clutch is pressed all the way to the floor, and the other foot begins to brake. One of two events then happen:

• The car ahead in fact comes to a complete stop. After that, of course, the transmission must be put in first gear and an ordinary start must be performed, albeit this is probably very gentle start, since the car isn't about to accelerate anywhere fast! It's useful to practice slow starts in a parking lot, which is another situation in which they are useful. The goal is to quickly get the car rolling in first gear and let the clutch out all the way, but then remain at the low speed. This requires gentle throttle work to only maintain the RPMs a bit above idle during clutch engagement. As the clutch grabs, pressure on the accelerator stays light: it is not increased as would be the case if the intent were to accelerate.

• The car ahead does not come to a complete stop, but instead speeds up. Now, a decision must be made whether to release the clutch, stay in second gear, or to downshift to first gear. This depends entirely on the vehicle's speed and how much torque its engine has at very low RPMs. In time, experience with that particular vehicle will furnish the driver with the requisite intuition. (If the speed is very slow, less than about 5 mph or 8 km/h, it's possible to downshift to first gear in just about any car, even ones which can handle moving at these slow speeds in second gear). If downshifting to first gear is necessary, it is done without bringing the car to a complete stop. Releasing the clutch in this situation is different from releasing the clutch in first gear during a start from a complete stop. The clutch can be released much faster in first gear if the car is slowly rolling forward at about walking speed.

After downshifting to first gear, if that was necessary, the car can stay in that gear, with the clutch fully engaged. Very slow crawling can be achieved in first gear. Once the crawling is fast enough to take the engine RPM's into the 1500-2000 range, second gear should be selected once again. Again, anticipation of traffic ahead is very useful. If cars are stopping ahead, creating a backward-propagating wave of stoppage, there is no point in switching to a higher gear. It's better to just continue to crawl in first, and then disengage the clutch and apply pressure to the brake when the stop comes. Better yet, if possible, the driver can allow the engine braking effect in first gear to create a larger gap to the next car, and use the space, together with the slow crawling capabilities of first gear, to avoid stopping entirely.

With practice, these shifts between first and second gear in heavy traffic become second nature, as will the traffic monitoring and anticipation which eliminates unnecessary stopping, shifting and clutch work.

The Canceled Stop

Situation: the driver is approaching an intersection where traffic is stopped at a red light. He or she is following the manual transmission technique for coasting to a stop. However, just as the approach is nearly complete, the light changes and it's not necessary to come to a full stop. The stop manoeuver is preempted, and a dynamic decision must be made about how to proceed. The key input to this decision is the vehicle speed, which determines what gear the vehicle should be in.

• If the vehicle almost came to a stop, and is rolling forward only very slowly less than 5 mph or 8 km/h, the driver may shift into first gear. At this speed, the driver should already have pressed the clutch all the way to the floor, in preparation for coming to a full stop. Because the car is rolling, the clutch can be released quite rapidly. (But if first gear is inappropriately selected at too high a speed, and the clutch is released rapidly, there will be a jerk!)

• If the speed is above approximately 5 mph or 8 km/h, but below around 20 mph or 30-35 km/h, the driver should select second gear, release the clutch fairly quickly and proceed.

• If the traffic change occurs above these speeds, resuming is possible in third gear. In fact, it's possible that the transmission is still in third gear and the clutch hasn't even been pressed down. In other words, it may be possible to just step on the accelerator and resume.

The tricky cases are the near-stops when the car is still rolling. The driver must select the correct gear based on speed, and be confident that a quick clutch release can be executed without stalling or jerking. The speedometer is of little use at these slow speeds. The driver, in fact, must not be staring at the speedometer and trying to reason about the correct gear. Rather, intuition for this must be learned through practice.

Troubleshooting

Stalling

When a vehicle's engine is turning at low speeds it is unable to provide much torque, and placing excessive demand on the engine will cause it to stop running suddenly, an event known as a stall. Stalling usually causes sudden jerking movements of the vehicle.

The following behaviours are likely to cause stalls:

• at a standstill, engaging the clutch too quickly, while the engine is turning too slowly;
• coming to a stop with the clutch engaged and the transmission in gear.
• trying to start from a standstill in high gear

If the driver stalls the engine, they should not panic. It happens to all beginners and even occasionally to experienced drivers, and it's nothing to be ashamed of. In order to get going again and not to hold up traffic, the driver can simply keep the brake and clutch depressed, then restart the engine (note that the key often needs to be turned back to its off position before the starter will operate again), select the correct gear if necessary, and then drive off.

If at any time the driver senses that the engine is about to stall, the clutch should immediately be depressed. If the driver gets scared or needs to come to a stop quickly, it is important to step on the clutch while instinctively hitting the brakes, otherwise the engine will probably stall.

The clutches in different vehicles vary in their sensitivity and range of movement, so even a very experienced driver in an unfamiliar vehicle can stall its engine a few times until he or she becomes familiar with its clutch.

Stalling due to loss of traction while braking

When decelerating, a driver will apply brakes and then disengage the clutch shortly before stopping (around 1000 RPM in 1st gear or somewhere above "walking speed" as above). In normal conditions with good traction, this is fine. However, on some surfaces, and depending on the severity of the braking, without an Anti-lock Braking System, the wheels can lock up. This can happen easily on slippery surfaces like snow, ice and loose gravel. The poor traction on such surfaces can prevent the momentum of the car from turning the wheels, which leaves the engine as the only real force for the brakes to oppose.

When this happens, the first priority is to bring the vehicle safely to a stop or to regain braking and steering control. See also cadence braking, an important skill for winter drivers without ABS equipped vehicles.

Grinding Gears

A grinding sound coming from a synchronized manual transmission during a shift is usually a sign of improper technique. Some hobbyist drivers blame the machinery: they claim that the synchro mechanism is worn, or there is some issue with the manual transmission lubricant. This comes up again and again in online automotive forums. In fact, the synchro mechanism would have to be completely gone for this to be true, and it's almost certainly not an issue with the lubricant.

Why does grinding happen in a synchronized transmission? It's because the overly zealous driver engages the clutch too fast, in parallel with moving the gearshift, in an attempt to minimize the overall shift time. Or, perhaps the driver is doing everything in the correct sequence, but failing to press the clutch far enough! Or, the driver has pushed the gearshifter very fast into the shift gate causing the synchronizer to be jammed up against the gear too quickly, and not allowed to do its job. Either way, the gear selector has already "passed through" the synchronizer, but not gone far enough for the teeth to actually engage. At this point, if the clutch is engaged, even slightly, the speed of the input shaft will change, and the synchronization will be lost. Since the selector has already been pushed through the ring, it's too late: the stick can be moved so that the teeth make contact. The result is grinding.

Quite possibly, there could be a problem with the clutch: perhaps it is not disengaging all the way when the pedal is being pressed to the floor. The pedal might need adjustment, or there is some problem with the hydraulics or mechanical linkage, or other problem with the clutch mechanism itself. But here we are assuming that there is no mechanical problem.

To avoid grinding, do the waltz: think 1-2-3. On the count of 1, press the clutch all the way down to the floor. On the count of 2, move the stick to the desired gear. On 3, release the clutch. To speed up the gear change, you must speed up these motions individually, and not "cheat" by trying to overlap steps 2 and 3. There is little room for that. In particular, the lever must be in the final position before the clutch moves off the floor. Where you can save time is by tightly combining 1 and 2. Push or pull on the stick while pressing the clutch, to get it moving as soon as possible. Practice the waltz: count 1-2-3 in your head. Try doing it very slowly, and then speed up the tempo.

To do a fast gear change without grinding, push the clutch pedal to the floor as fast as possible, in advance of moving the stick, but start moving the stick even before the clutch hits the floor. The clutch should be all the way down as the stick passes through the neutral position to the other gear, and should remain floored. Move the stick as fast as possible from one gear to the other, using speed and force. You should feel a resistance followed by a click; that's the resistance of the synchro, which needs time to do its job before allowing the selector to proceed. Finally, release the clutch. This is the slowest part of the transaction, but with practice, it can be sped up significantly.

The common mistake that causes grinding is not moving the stick fast enough before releasing the clutch; failing to coordinate the two motions. Sometimes drivers complain about grinding during steep gear changes, when the engine is revved to a high RPM in the lower gear. The synchro has to do more work to slow down the input shaft of the transmission to match up the next gear! This takes more time, but the driver is not adjusting for it. He or she is not waiting for the lever to pop through the synchro, and is releasing the clutch using a rehearsed timing, independently of what is going on in the gearbox. The foot doesn't know what the hand is doing and vice versa! The foot must be trained to wait for the hand to complete the gear selection.

Another situation in which grinding can be heard is when placing the transmission into reverse from a stopped position, e.g., when leaving a parking space. Grinding occurs here in part because reverse is often not a synchromesh gear. If one does not leave the transmission in reverse or a forward gear when parked, it is likely that s/he will hear grinding in the transmission when shifting into reverse no matter how far the clutch pedal is held in when shifting. To avoid grinding in reverse, one must "clear the gate": first place the gear shift into a forward gear, then shift into reverse. This will eliminate any grinding that is heard. It works because all gears have the same speed when the car is stopped. On most 5-speed synchromesh transmissions, the gates will lock out a shift from 5th gear down into reverse as a safety feature; therefore, place the shifter into another forward gear before shifting into reverse. Some old cars have synchromesh on the upper gears but not on 1st, so this procedure should be used every time they are started from a stop. (Some old BMWs had synchromesh on first, for downshifts, but still crunched starting from a stop.)

One last note: the transmission oil can make a difference if the shift is being done improperly. A lubricant that doesn't have the proper friction additives will cause the synchro to take more time, giving rise to more opportunity for premature clutch release. This is why some technically inclined drivers report experiences like "I switched my manual transmission fluid from brand X to brand Y and now I get more (or less) grinding". Some cars also shift more easily when the transmission oil has warmed up; Mazda Miatas and Volkswagen Passats are particularly known for this.

Advanced techniques

This section discusses performance driving techniques, which may be detrimental to the life of the power train and other components of the vehicle.

Easing out of gear (no clutch)

It's possible to shift the transmission into neutral without using the clutch, and some of the other advanced techniques below call for this. However, taking the transmission out of gear may require a great deal of force, because the dog teeth are held in place by great torque between the input and output shafts. Pulling the teeth apart forcefully when they are jammed together by torque wears them. The force required is also demanding on the gear selector linkage and shift forks.

However, when the car is coasting to a stop, the engine eventually reaches a sufficiently low RPM at which there occurs a relaxation of the torque through the transmission. This relaxation can be perceived as a subtle change in the motion of the car; near a certain RPM value, the compression braking effect suddenly disappears, resulting in the sensation of a very slight forward jolt of the vehicle. This loss of the braking effect literally feels like a relaxation; the engine is neither propelling nor hindering the car's motion, because its idle speed is approximately matched to the rotation of the transmission's input shaft. In this condition, it may be acceptable to exert a light tug or push on the gear lever to see whether it can be gently coaxed out of gear. If it pops out easily, there is likely no harm done. On the other hand, if there is resistance, it can be relieved right away by pressing the clutch.

If the transmission remains in gear and the RPM drops further, the relaxation effect will disappear; the idle control mechanism will struggle to keep the engine turning, exerting torque on the slowing transmission. Sometimes the relaxation point is only very brief, or does not occur at all: for instance, when coming to a stop against an incline. The vehicle then decelerates due to gravity, regardless of the compression braking effect. Consequently, there will be only a tiny moment during which the transmission's speed will match the engine idle closely enough. The relaxation point may be located by exerting a continuous gentle force on the gear lever as the vehicle slows down.

Similarly, exerting continuous gentle force over a short period of time and lifting off the throttle (if accelerating), or blipping the throttle (if decelerating) will result in a smooth, clutch-free gear change to neutral. This is because you have created, via modulation of the throttle, a point where there was no torque holding the dog teeth together; if you were accelerating, lifting off for a moment produces a slight deceleration. In between accelerating and decelerating, there was a point where, as noted above, both the driving and the driven shafts, gears, dog teeth, etc. were spinning at the same speed, so there was no torque holding the dog teeth together, so you were able to move to neutral without the clutch.

Power shifting (a.k.a. speed shifting)

This is an advanced technique that gives a speed boost to the car when upshifting. This should only be used in racing applications (and probably only in very short races), as it is very hard on drivetrain components, especially if done improperly. Even done properly, it generally puts undue stress on the drivetrain, and shortens the lifespan of the driveline components.

To perform a power shift, keep the gas pedal on the floor (instead of lifting) while pushing in the clutch. At the same time, quickly shift to the next gear. Quickly re-engage ("pop") the clutch as soon as the new gear is selected. If done properly, the car will receive a "bump" in acceleration (due to the jerk of the decelerating engine) as the clutch is re-engaged. If done improperly, it can result in engine or transmission damage, sometimes catastrophic.

Heel-and-toe

While decelerating, the technique of heel-and-toe shifting allows advanced drivers to maintain pressure on the brake pedal while simultaneously "blipping" the throttle to aid downshifts. This allows the car to remain flat and "level" while entering or exiting a turn. This is done by using the right foot to control both the brake as well as the gas pedal at the same time, normally done by keeping your foot at an angle, thus the term Heel-and-toe.

Double clutching

"Double-clutching" (also known as "double-declutching" in Europe) is an old technique that dates from before the days of synchromesh gear boxes. It can make downshifting (and arguably upshifting) smoother and can reduce transmission wear. It involves depressing the clutch and dropping into neutral, releasing the clutch, using throttle to match revs for the gear to be selected, depressing the clutch again and selecting the new gear. The action (which sounds more complicated than it really is) uses the engine to spin up the input shaft to more closely match the next gear selected hence creating smoother shifts and reducing wear on synchromesh systems. If the car is equipped with a tachometer, it may be used to help find the right engine speed. Some types of unsynchronized manual transmissions require double-clutching. These transmissions may be found in some older vehicles and race cars, as well as on large trucks, especially tractor-trailers. When we say require, if you mishap and pick a wrong gear, or take too long and are unable to double-clutch and match both halves of the transmission, you come to a stop and start all over again.

Double-clutching on a synchronized gearbox is unnecessary in most driving situations. Moreover, it is possible that an unskilled driver may second-guess something that the machine is designed to do automatically, and can cause more harm than good. A true unsynchronized transmission is unforgiving to mismatched speeds, requiring a great deal of precision from the driver. A synchronized transmission will allow the driver to get away with sloppy double-clutching, and an unskilled driver may end up causing more harm by not matching the engine speed properly.

However, even with a synchronized gearbox, double-clutching under skilled hands is desirable when shifting down to the lowest gears. The synchronizer, particularly the one for the second gear, receives much abuse, as the speed differential it has to manage is usually the greatest. It is indeed usually the second gear synchronizer that fails first. Some recent Honda manual transmissions incorporate a triple-cone synchronizer in the lowest gears for extra durability.

Many transmissions until recently did not have a synchronizer on the first gear. It is therefore necessary to double-clutch when downshifting into the first gear, though such instances are rare. Some transmissions today still do not have a synchronizer for the reverse gear, requiring that you come to a complete halt before shifting into reverse (see the "Grinding gears" section above for further implications of this). Double-clutching is of course impossible, as you cannot reverse the direction of the engine rotation. You must simply wait for the car to come to a halt and engine revs to drop to idling.

Single clutching

A downshifting technique similar to a cross between double clutching and shifting without the clutch. The transmission is taken out of gear while the clutch is still engaged. The accelerator is then 'blipped' to bring the input shaft to the correct speed, the clutch is disengaged, the lower gear is selected and the clutch is engaged again. This is a fairly common racing technique.

Some drivers also use an even faster method than single clutch downshifting, which is also the method used in conjunction with heel-toe downshifting. The clutch is disengaged, the driver selects the new gear while "blipping" the throttle up to bring the engine to approximately right speed and then the clutch is engaged again. In other words, as the transmission's synchro changes the rotation of the input shaft during the gear selection, the driver simultaneously adjusts the engine revolution speed. The clutch can be released very quickly if the difference in rotation between the clutch disk and flywheel is small, so this gear change is likely the fastest technique on a synchronized tranmission. Some experienced drivers perform this revolution matching almost instinctively. During the downshift, as the gear selector passes between the gears, they hit the throttle to bring the engine revolutions up. The resulting gear change is not only faster, but it can be much smoother, as well as reduce the wear on the clutch.

Shifting without the clutch

It is possible to shift gears without using the clutch at all, by careful throttle manipulation. When transmissions were unsynchronized this was usually the easiest method, and still works in modern cars, although it requires a lot more practice than the usual methods described above.

Although the technique works in synchronized gearboxes, it is inappropriate in nearly all circumstances. A synchronized gearbox has a small clutch called a synchronizer (or "synchro") in every forward gear which brings the input and output rotation to the same speed before allowing them to engage. Like the main clutch, these synchronizing clutches use friction. These synchronizing clutches will allow for a margin of error when engaging without the main clutch. If the engine speed is somewhat too high or too low, the synchro will essentially take on the job that the fully engaged main clutch isn't doing. However, a synchro ring is not intended to do the job of a main clutch. Its job is to spin up or spin down just the input part of the transmission that is assumed to be disconnected from the engine. It is not intended to speed up or slow down the entire engine. Such experimentation done on a regular basis will prematurely wear out the synchro rings, which will have to be replaced.

On cars with a freewheel, such as the older SAAB with a two-stroke engine, shifting without the clutch is standard procedure. But actually, the freewheel is a form of clutch: one that is disengaged whenever the input rotation is slower than then output rotation. One must disengage the freewheel by allowing the engine revolutions to drop, which is analogous to pressing the clutch pedal.

Starting the vehicle without an electric starter

Should the starter fail to operate due to a dead battery, electrical fault, or a defect in the starter itself, the vehicle may be startable via momentum. The energy to move the vehicle initially can be supplied either by gravity (if the vehicle is parked on a hill), or by people pushing. To start the vehicle on a hill if the vehicle is facing downhill: place the transmission in second gear with ignition key in the "on" position. The clutch should be disengaged (clutch pedal pressed down), release the brake, and allow the car to roll. When it reaches about 10 km/h, release the clutch slowly, as if executing a steep downshift. The car will slow down due to compression braking as the engine spins up. If ignition and fuel are supplied to the engine, it will start. If it does not succeed the first time, try again with more speed. If it still doesn't work, whatever is preventing the engine from starting is also preventing it from running.

The techniques for starting while facing downhill and push-starting are similar. A single person may be able to push-start a compact car or mini-truck; it may take several people to start a larger vehicle. Use reverse gear for starting while facing uphill.

Push starting is easiest and safest with at least two people. The assistants push, while the driver, sitting in the driver's seat, carries out the remaining steps. Push starting on level ground is more difficult and dangerous for a single person. He or she must push the car, and then when enough momentum is gained, jump into the driver's seat of the moving vehicle to complete the start. The driver must also be prepared to jump into the seat at any time to stop the vehicle. Therefore, it is necessary to push the car from the side, with the driver's door open. The driver is positioned behind the open driver's door, and applies force to a frame member of the car body, such as the windshield post or roof post. From this position, one hand can reach the steering wheel, and it's possible to jump into the car quickly.

'Important notes'

• If the engine turns over when the ignition is activated, but does not start, then the starter is working, and neither push-starting nor jump-starting will start the car. The car needs fuel or repair.

• If the starter failure was due to a discharged battery, it will recur unless the engine runs long enough to sufficiently recharge the battery.

• If the starter failure wasn't due to a discharged battery, it will certainly recur. The car will have to continue to be push started, and must be taken to a mechanic to have the starter problem identified and repaired.

• The alternator in the car is not meant to charge deeply discharged batteries. A proper battery charger includes a current limiting circuit which "trickle charges" the battery. A deeply discharged battery places a load on the car's charging system. Put the battery on a trickle charger at the earliest opportunity.

• If the battery is completely flat, push starting may not work, because modern cars have an alternator which does not contain permanent magnets. It has coils which require a small field current to generate a magnetic field.

• Check the condition of the battery first. Some batteries have an hydrometer "eye". If the eye is green, dark green or dark, attempting to push start should be okay. If it's clear or yellow, indicating an insufficient fluid level, don't jump or push start. The battery needs distilled water, and should not be charged. If it's a sealed battery, it should be replaced, since there is no means to add fluid.

• If the battery is frozen, do not push start or jump start the vehicle. The battery must thaw first. Frozen batteries should not be charged.

• Read the owner's manual of the vehicle for any special instructions regarding jump starting, and follow whatever reasonably applies to push starting also.

• If the car has power brakes or power steering, these will not function during the push start until the engine starts. If the car is being started by rolling down a hill and the engine fails to start, a lot of extra brake pressure will be needed to stop it, and extra force on the steering wheel will be needed to steer around any obstacles.

• Do not push the vehicle with another car or truck; the bumpers may slip, damaging both vehicles.

• Jumping into a moving car requires a modicum of athletic ability, coordination and daring.

• Pushing a car is a strenuous athletic effort. It must be done intensely in order to give the car maximum possible momentum in the shortest distance, which carries the same risks of over-exertion and injury as any intense exercise. It may be wise to first perform some light warm-up exercises and stretches involving all of the major muscle groups of the body.

• When riding a motorcycle, the sudden lock of the back tire when releasing the clutch can throw you in many directions. Drag your feet on the ground as to maintain balance.

Compression braking

This is also called "engine braking": the use of the engine's internal resistance to slow down the vehicle, or keep it from accelerating down a hill. This is done by lifting your foot off the throttle when the engine is running at a speed sufficiently above idle. Shifting the car into a lower gear can amplify the effect.

On the one hand, some feel that you abuse your manual transmission and engine by "engine braking". They feel that you should downshift only when you anticipate that the car will be in a lower speed for some time, not when coming to a full stop. Some feel that the reason why you must keep the car in gear while slowing down or stopped but with the clutch disengaged is for emergency maneuvers, for it will give you the extra time to escape a pending accident. In this case, downshift late, allowing the car to slow to a pretty low engine RPM's before shifting down. This viewpoint says that using the manual transmission to stop the car is inappropriate under normal driving conditions. Simply put, when using the engine to slow the speed of the transmission, the clutch and synchronizers are unnecessarily being worn out for what the car brakes are designed to do. In comparison, the clutch typically costs around US$1,000 to fix as opposed to US$300 for new brake pads and installation. (However, clutches typically last far longer than brakes, so the two cannot be directly compared on price alone.) The method is provided only because one may find it occasionally necessary or useful to use engine braking (when one needs to decelerate more quickly than usual, for instance). If decelerating towards a full stop while in an upper gear, such as 4th, a downshift to a lower gear should be made, as this increases the time that a gear is engaged, therefore keeping the brake and power steering servos engaged and so power is supplied. Coasting time should be kept to a minimum using effective and well-timed downshifts.

On the other hand, some feel that engine braking is relatively harmless to the engine and transmission. Smooth double clutching when down shifting will minimize wear on the clutch and synchronizers. Not picking gears to excessively rev the engine more than 3000rpm, yet not so slow you lose oil pressure. Stay above 500rpm to achieve sufficient oil pressure. As for engine wear, piston rings will be worn more, but keeping the RPM in a relative range will prevent them from stress of expanding and contracting at high speeds with the up and down movement of the piston. Also during deceleration the engine creates a vacuum in the cylinders which pull a very small amount of oil past the rings, increasing protection. This, combined with the fact that the forces involved are typically less than those normally seen during acceleration lead some to conclude that it will make no real difference in the lifetime of the engine and transmission. There is a situation when engine braking is truly called for: going down steep hills which are also very long, and for whatever reason, it is undesirable to pull over and stop the car. Braking downhill for a long time can overheat the brakes leading to brake-fade or, in extreme cases, failure. A combination of gearing down and using the brakes is safer. But heat can be dissipated from brakes also by pulling the car over and letting it stop for a while, effectively dividing the long hill into a sequence of shorter ones.

Engine braking(for large trucks) is illegal in some cities.

A Jake Brake modifies the characteristics of an engine with a push of a button to stop a vehicle.. A special modification is installed in the valve train. In short, when engaged, the force used to compress the air is used to slow the vehicle, then at a precise time, just before the piston reaches Top-Dead center, the exhaust valve is pushed open, expelling the air. On trucks with performance or no mufflers a distinctive, and sometimes painfully loud noise is made as the truck slows, and the pitch changes as the driver shifts to lower gears.

A true engine brake.

External links

• Jake brake on the English Wikipedia